Ch2_BME520_Concepts and Requirements.pdf

Biomedical Devices Design and Troubleshooting (BME520 ) Chapter 2: Concepts and Requirements Claudio Becchetti, 1th Edition Dr. Qasem Qananwah 7/28/2024...

Biomedical Devices Design and Troubleshooting (BME520 ) Chapter 2: Concepts and Requirements Claudio Becchetti, 1th Edition Dr. Qasem Qananwah 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 1 Chapter 2: Concepts and Requirements BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department  Chapter 2: Concepts and Requirements 2.1 Introduction Medical instruments rely on specific physiological properties to infer the health condition of specific parts of the human body. The first design step is therefore focused on understanding on which concept medical instruments rely on to assess health. The second design step implies the definition of what the medical instrument has to do so that all the manufactured products are safe and effective. The ‘whats’ that a product is intended to do are formalized through requirements. BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department  Chapter 2: Concepts and Requirements Part I: Theory Introduction Four distinct ways through which technology takes place in healthcare delivery: level 0: both diagnosis and therapy are virtually unassisted by technology: the diagnosis is drawn by direct observation and the therapy may perhaps be provided manually. level 1: technology assists in the diagnosis, that is, it provides clinically relevant parameters to help the practitioner determine the presence of a pathology. In addition, technology may help treatment, for example, by improving the effectiveness of the practitioner’s therapeutic intervention. 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 4  Chapter 2: Concepts and Requirements Part I: Theory Introduction Four distinct ways through which technology takes place in healthcare delivery: level 2: technology intervenes at the decision/interpretation level, that is, by proposing a possible diagnosis that can be used by the practitioner. This can be done not only through the parameters collected in the diagnosis stage, but also through other patient-related information collected and interpreted by the information processing system. level 3: the technology integrates all the information gathered from the patient, it interprets this information (e.g., through expert systems) and delivers the therapy based on the results of the interpretation. At this level, we may say that biomedical technology is the master in the healthcare delivery process. 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 5  Chapter 2: Concepts and Requirements Part I: Theory Introduction WHAT IS A MEDICAL DEVICE? A medical device (MD) is any instrument, appliance, apparatus, material or other article, whether used alone or in combination, including the software necessary for its proper application, intended by the manufacturer to be used for human beings 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 6  Chapter 2: Concepts and Requirements Part I: Theory Introduction medical devices may be organized into three different groups: diagnostic equipment, where information flows from the patient to the technology therapeutic equipment, where the flows is the other way around – the treatment is performed by the machine on the patient (this includes rehabilitation equipment) information processing systems, where the information gathered is interpreted to assist in the clinical decision process. 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 7  Chapter 2: Concepts and Requirements Part I: Theory Introduction We will focus on diagnostic equipment that is represented as a device model that performs the following tasks: 1. sense the patient information 2. transform this information into an electrical signal 3. remove artifacts, and sources not meaningful for diagnostic purposes, from the input signal 4. extract parameters and indexes that have a physiological meaning and can be profitably interpreted by the clinician practitioners to infer health condition 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 8  Chapter 2: Concepts and Requirements Part I: Theory Introduction Medical practice shows that instrumentation products that did not take into account the ‘doctor–patient in the loop’ often end up as a market failure. So, policies are recommending that innovative products increasingly be patient/user centered and demand driven, focusing on healthcare needs. Medical device requirements must encompass how the instrumentation is used by doctors and technicians, and perceived by patients, because doctors, technicians and patients are essential components of the diagnostic process 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 9  Chapter 2: Concepts and Requirements Part I: Theory Introduction A reasonable medical instrumentation approach is (Problem to be solved): 1. define the medically relevant problem 2. define the measures to detect the problem 3. define the instrument to detect the problem 4. define how the healthcare service that uses the instrument is organized, taking into account the patient/doctor in the loop. 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 10  Chapter 2: Concepts and Requirements Part I: Theory The Medical Instrumentation Approach Figure 1 Information flow from patient to instrument 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 11  2.2 The Medical Instrumentation Approach The process can then be summarized as follows: 1. The presence of a pathology determines a change in the function or the anatomy of an organ in a specific domain (e.g., size, voltage amplitude, shape, pressure). 2. The instrument measures a variable in a different domain. 3. The modifications to this variable are projected into this new domain, where variables can be corrupted by the presence of noise and artifacts. 4. Through the help of hardware devices and software solutions this representation domain helps clinicians answer the questions of whether the pathology is present and to what extent. BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department  Chapter 2: Concepts and Requirements Part I: Theory The Medical Instrumentation Approach In the design of a biomedical instrument, the process depends on the inputs that comes from a clinical requirement. The biomedical instrument will therefore be designed including a number of variables at least equal to or better than what is required to detect the change with sufficient accuracy. 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 13  Chapter 2: Concepts and Requirements Part I: Theory The Medical Instrumentation Approach A biomedical instrument corresponding to an established way of capturing data, these requirements may be determined by the clinical specialist and their recommendations. Most of the medical devices grouped according to the Global Medical Device Nomenclature (GMDN) refer to recommendations given by the ECRI Institute 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 14  Chapter 2: Concepts and Requirements Part I: Theory The Medical Instrumentation Approach Table 1 EEG recommendation adapted from ECRI 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 15  Chapter 2: Concepts and Requirements Part I: Theory The Medical Instrumentation Approach The requirements (of MD) usually entail a group of technical specifications that can be summarized as follows: o Specifications related to the quality of captured data (e.g., sensitivity, frequency range, resolution, intrinsic noise, linearity, reliability) o Specifications related to the processing and visualization of the data o Specifications related to the usability of the system, and to the range of choices that the operator can handle to optimize the recording in the specific case o General specifications, such as size, weight, power requirements. 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 16  Chapter 2: Concepts and Requirements Part I: Theory The Medical Instrumentation Approach When, the medical instrument to be designed is not included in the range of the state-of-the-art devices (inputs are unknown), specifications needs to be heuristically determined by the designer and then validated according to the applicable regulatory framework. In this case, it must be considered that each source of uncertainty originating from the instrument will be propagated through all sections of the medical system itself in a way that needs to be kept under control, 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 17  Chapter 2: Concepts and Requirements Part I: Theory Extraction of Physiological Parameters The presence of pathology may result in a modification of the function or the anatomy of an organ ➔ This necessitate diagnosing to find the modifications associated with the disease This modification can either be o directly observed o indirectly estimated from a number of measurable units 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 18  Chapter 2: Concepts and Requirements Part I: Theory Extraction of Physiological Parameters Example: anatomical modification of the lungs, associated with the presence of a malignancy in the lung directly observed: using specific diagnostic imaging devices e.g X-ray..etc Alternatively, the modifications of the respiratory functions driven by the malignancy in the lung indirectly estimated: by using of pulmonary function analyzer 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 19  Chapter 2: Concepts and Requirements Part I: Theory Extraction of Physiological Parameters The quantification of these modifications is the main objective of a medical instrument. 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 20  Chapter 2: Concepts and Requirements Part I: Theory Extraction of Physiological Parameters Dimensionality of the variable to be measured: point parameters (e.g., blood pH) 1-D waveforms, as a function of space or time (e.g., EEG, ECG) 2-D waveforms, as a function of 2-D space, or changes over time of a 1-D space variable (e.g., an X-ray image) 3-D waveforms, which depict the behavior of a variable in 3-D space, or the changes over time of a 2-D projection (e.g., computer tomography CT) 4-D waveforms, which describe the behavior over time of a variable represented in 3-D space (e.g., time-resolved cardiac magnetic resonant imaging). 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 21  Chapter 2: Concepts and Requirements Part I: Theory Extraction of Physiological Parameters A pathology is usually associated with a set of parameters: from the measured variables: relevant points in the waveforms, such as in the case of ECG waveforms, where amplitudes, distances over time and ranges are used to determine the presence of a pathology, from ensemble parameters, extracted with the use of some statistical method, and represented in the domains of interest, such as in the case of quantitative EEG analysis, where second-order moments are calculated from the raw EEG data and classified in the frequency domain, and from some simplified function calculated from the raw data, when it is deemed easier to gather data in the simplified domain than in the original one, such as in the case of the quantification of apnea based on the bispectral index (BIS), calculated to enlighten phase couplings in EEG rhythms 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 22  2.2 The Medical Instrumentation Approach The process can then be summarized as follows: 1. The presence of a pathology determines a change in the function or the anatomy of an organ in a specific domain (e.g., size, voltage amplitude, shape, pressure). 2. The instrument measures a variable in a different domain. 3. The modifications to this variable are projected into this new domain, where variables can be corrupted by the presence of noise and artifacts. 4. Through the help of hardware devices and software solutions this representation domain helps clinicians answer the questions of whether the pathology is present and to what extent. BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department  Chapter 2: Concepts and Requirements Part I: Theory Extraction of Physiological Parameters Table 2 Physiological 1-D parameters characteristics 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 24  Chapter 2: Concepts and Requirements Part I: Theory Extraction of Physiological Parameters Table 2 Physiological 1-D parameters characteristics 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 25  Chapter 2: Concepts and Requirements Implementation Requirement Management The design team must define what the system must do and how well it must performs its functions. 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 26  Chapter 2: Concepts and Requirements Implementation Requirement Management Figure 2: Requirement process model 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 27  Chapter 2: Concepts and Requirements Implementation Requirement Management The more the requirements, the more the cost, development time and risks. Therefore, care must be taken in the requirement review process. The requirement management is a continuous process throughout the project and updated during the various steps of product development (speed up to maintain team collaboration) The requirement analysis is an iterative and incremental process 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 28  Chapter 2: Concepts and Requirements Implementation Medical Instruments Requirement and Standards A possible model for generating requirements for a new product Figure 3: Requirement generation scheme. 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 29  Chapter 2: Concepts and Requirements Implementation Medical Instruments Requirement and Standards Table 3: IEC/EN 60601-X main standards 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 30  Chapter 2: Concepts and Requirements Implementation Medical Instruments Requirement and Standards It is recommended that a specific set of critical requirements has to be continuously monitored throughout the project: 1. signal performances (e.g., frequency response) 2. electrical safety performances (e.g., leakage current, harmful energies) 3. electromagnetic compatibility (EMC) performances 4. mean time between failures (MTBF) 5. production cost. 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 31  Chapter 2: Concepts and Requirements Implementation Medical Instruments Requirement and Standards Why we use standards through the design process? They are used since standard… 1. are appealing from a customer marketing point of view 2. guarantee product quality for the customer 3. create a product competitive advantage 4. allow for saving in product industrial research 5. reduce risks. 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 32  Chapter 2: Concepts and Requirements Implementation Medical Instruments Requirement and Standards For some more common medical devices, there are also standards that define the minimum essential performance requirements. These performance standards may greatly reduce the research effort. 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 33  Chapter 2: Concepts and Requirements Implementation Medical Instruments Requirement and Standards Performance Standards such as AAMI EC 11 (AAMI, 1991) for ECG This standard establishes minimum safety and performance requirements for electrocardiographic (ECG) 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 34  Chapter 2: Concepts and Requirements Implementation Medical Instruments Requirement and Standards Section 2.11 gives an example for all the procedures mentioned in this chapter 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 35  Implementation:: 2.11. ECG Requirements Requirements will be identified with the label ‘RX’. The following R1 and R2 are the first main requirements BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department Implementation:: 2.11. ECG Requirements BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department Implementation:: 2.11. ECG Requirements BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department Implementation:: 2.11. ECG Requirements BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department Implementation:: 2.15. Requirements Related to Measurements BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department Implementation:: 2.16. Safety Requirements BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department Implementation:: 2.17. Usability & Marketing Requirements BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department Implementation:: 2.18. Environmental Issues BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department  Implementation: 2.19. Economic Requirements The overall production cost is decomposed into 1. materials to produce the ECG as specified in requirement R 2 acquisition unit 10 reusable electrodes patient cable software application running on the PC packaging instruction manual PC cable connection. 2. Man hours and services to produce directly the product: to assemble and test the acquisition unit to prepare the overall package. BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department  Questions ???? 7/28/2024 BME520: Biomedical Devices Design and Troubleshooting Biomedical Systems and Informatics Engineering Department 46